Voice over Internet protocol (VoIP) refers to the ability to transmit voice signals over computer networks using the Internet protocol (IP). Voice signals are first digitized to transform the analog input into a stream of digital data. Such data may or may not be compressed, as may be required by the specifics of the system being used and the capabilities it offers. The data, whether compressed or uncompressed, is then transmitted over an IP network by first formatting the voice data stream into multiple discrete packets. In a VoIP call, an originating voice endpoint quantizes an input audio stream into packets that are placed onto an IP network and routed to a destination voice endpoint using standard IP routing techniques. The destination voice endpoint restores packets into a digital audio stream that resembles the input audio stream. Compression and decompression of voice is done by using a codec (coder/decoder) implemented in hardware, software or combinations thereof, algorithms which are applied on the quantized digital audio stream to reduce the communication bandwidth required while transmitting, and restore the compressed data when receiving.
FIG. 1 is a block diagram of an example VoIP network 100. Network 100 consists of points of presence (PoPs) 110-1 and 110-2, voice endpoints 120-1 and 120-2 (also termed “voice gateways”), and IP network 130. Voice endpoints 120-1, 120-2 are the convergence points of VoIP network 100 and provide an interface between the packet side of IP network 130 and switch 140, as further explained below. Voice endpoints 120-1, 120-2, transform voice streams into packets that are placed onto IP network 130. Packets are routed to a destination endpoint 120-2. Destination endpoint 120-2 transforms the packets back to a voice data stream.
PoPs 110-1 and 110-2 include standard telecommunication switches 140, which may include but are not limited to Class 5 Switches or others used in the conventional public switched telephone network (PSTN). Switches 140 receive various voice and voice-like sources, including but not limited to voice telephone calls, analog modem communication, and facsimile (fax) transmissions.
IP network 130 includes routers 132-1, 132-2, 132-N, which are capable of transferring packets according to TCP/IP protocols. These routers are not configured to perform or capable of performing quality of service (QoS) measurements, or control packet traffic. When transferring a voice call through a certain path in network 100, if a router 132-1 determines that the path is overloaded, then there are no options to reroute the voice call through an alternative path during the call session. In order to reroute a voice call to different path, there is a need to change the routing table in one or more of the routers 132-1, 132-2, 132-N.
Packet flows that are transmitted as part of VoIP service are well known to be highly sensitive to latency, jitter, loss, congestion, and other qualitative characteristics of the network. VoIP networks are based on existing IP networks and therefore cannot guarantee the quality level required for such services. More specifically, this inability is a result of limitations in the original IP network architecture, which was designed for the efficient transmission of data but with little to no consideration for real-time applications, i.e., applications such as voice where timely delivery of packets of data is paramount.
In order to provide better VoIP services, IP network technology must be improved in areas such as latency, disconnected calls, network congestion, packet loss and the limited control over the network. It would be advantageous to provide solutions that resolve the problems with IP network quality in a manner that would allow the use of the vast infrastructure already existing. Moreover, such a solution should also be able to efficiently and effectively transfer audio, video or any stream of data over an existing IP network.
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.